One of the most common problems encountered in the cooking of baked goods in an ordinary gas fueled or electrically powered oven is uneven heating, resulting in parts of the baked items being more cooked than other parts of the item. For example, in the case of cookies, the periphery of the cookie is often charred or browned, while the rest of the cookie is properly cooked.
In an attempt to provide a remedy for this problem, a number of partially effective solutions may be proposed. For example, the lumps of dough which melt to form the cookies may be placed closer together on the baking sheet, thereby causing them to melt into each other and form one large mass. In such a manner, the majority of the peripheral area of the cookies is eliminated and the resulting large planar cookie may then be cut to form individual cookies. However, the periphery of this large cookie will still suffer from the same problems and is thus likely to be overcooked. In addition, because of the large size of the central area of the larger cookie, prolonged baking may be required and the browing on the periphery of the larger cookie may be thus severe in magnitude and cover a wider area of the periphery.
As an alternative, the baker may choose to remove the cookies from the oven before the edges become too severely burned. However, this results in a compromise of the cooking time for the center of the cookie and, may result in a doughy, undercooked and unacceptable cookie center.
Applicant has determined the above problems to be the result of an interaction of heat insulative, heat conductive, and evaporative phenomena. In particular, during the course of cooking, the lump of dough rests on top of a cookie sheet having a thickness typically on the order of 0.035 inches. The cookie is subjected to the hot air in the oven both directly on the top of the cookie and through the pan on the bottom of the cookie. Because of the thinness of the cookie sheet, heat conduction to the bottom is excellent. Simultaneously, the cookie is subjected to cooling due to the evaporation of moisture and other vaporizable materials in the raw dough. In addition, the portion of the cookie sheet between the cookies absorbs heat from the hot air in the oven. Because the portion of the cookie sheet underneath the cookies is relatively cool due to the evaporation of moisture from the cookie, a temperature gradient exists between that portion of the cookie sheet underneath the cookie and the remaining portions of the cookie sheet. Accordingly, there is a resultant heat flow from the exposed portions of the cookie sheet to the portions underneath the cookie. These exposed portions thus act as heat collectors.
The first portion of those portions of the cookie sheet underneath the cookie to receive the heat collected by the exposed portion of the cookie sheet is that area which immediately underlies the periphery of the cookie. The periphery of the cookie is, in turn, relatively cool due to evaporation. The heat is thus conducted to the cookie from this peripheral portion of the cookie sheet, heating the peripheral portion of the cookie, causing more evaporation of moisture from the peripheral portion of the cookie resulting in cooling of the peripheral portion of the cookie sheet underlying the peripheral portion of the cookie and, accordingly, the conduction of more heat to the peripheral portion of the cookie sheet.
During the course of cooking, the moisture content of the periphery of the cookie is thus reduced dramatically as compared to the moisture content of the central portion of the cookie. As cooking progresses further, almost all moisture is depleted from the periphery of the cookie and the application of heat to the periphery of the cookie, both from its underside and its topside, results only in oxidation of the ingredients and resultant charring or browning of the periphery.